feat(Nimble): New Flush Policy Implementation With Chunking (facebookincubator#14846)

Summary:

X-link: facebookincubator/nimble#240

This is an implementation of the new chunking policy described in this [doc](https://fburl.com/gdoc/gkdwwju1). It has two phases:

**Phase 1 - Memory Pressure Management (shouldChunk)**
The policy monitors total in-memory data size:
*  When memory usage exceeds the maximum threshold, initiates chunking to reduce memory footprint while continuing data ingestion
*  When previous chunking attempts succeeded and memory remains above the minimum threshold, continues chunking to further reduce memory usage

**Phase 2 - Storage Size Optimization (shouldFlush)**
 Implements compression-aware stripe size prediction:
*   When chunking fails to reduce memory usage effectively and memory stays above the minimum threshold, forces a full stripe flush to guarantee memory relief
*   Calculates the anticipated final compressed stripe size by applying the estimated compression ratio to unencoded data
*   Triggers stripe flush when the predicted compressed size reaches the target stripe size threshold

`shouldChunk` is also now a separate method required by all flush policies. We updated all previous tests and code references

NOTE: The Velox repo change here is just test copied into an experimental directory that references the flush policy.

Differential Revision: D81516697

Author: macvincent

velox/experimental/wave/dwio/nimble/tests/NimbleReaderTestUtil.cpp

@@ -346,7 +346,8 @@ std::vector<std::unique_ptr<StreamLoader>> writeToNimbleAndGetStreamLoaders(
   writerOptions.minStreamChunkRawSize = 0;
   writerOptions.flushPolicyFactory = [] {
     return std::make_unique<LambdaFlushPolicy>(
-        [](const StripeProgress&) { return FlushDecision::Chunk; });
+        [](const StripeProgress&) { return false; },
+        [](const StripeProgress&) { return true; });
   };
 
   std::vector<std::unique_ptr<StreamLoader>> allStreamLoaders;